Bottle inspection apparatus

ABSTRACT

An integrated photocell device for bottle inspection comprises a multiplicity of inspection photodiodes and a level sensing photodiode, which measures the average light transmission through a bottle, arranged in a suitable array for scanning an area of a bottle to be inspected. The level sensing diode is in the form of a grid distributed over the photocell device and the inspection diodes are disposed within the grid. The inspection diodes are each connected in an electrical circuit which is adapted to be triggered by a pulse applied thereto and to restore to its initial state within a time determined by the intensity of the illumination of the photodiode. The individual inspection circuits are connected in parallel to a load resistor, the output voltage across which drops to zero when all the circuits have restored to their initial states. The level sensing diode is connected in a similar circuit to each inspection diode and is connected to a separate load resistor. Means is provided for comparing the times taken for the two output voltages to return to zero, after the application of a pulse, in order to determine whether or not a bottle being scanned by the device should be rejected as being dirty or faulty.

United States Patent 1191 Poynton et al.

[ 1 Apr. 10, 1973 15 1 BOTTLE INSPECTION APPARATUS [75] Inventors:Bertram George Poynton, Bromham; Terry John Rich; Jeffrey JeromeSainsburyyboth of Kempston, all of England [73] .Assignee: Fords(Finsbury) Limited, Bedford,

England 22 Filedr Dec.21, 1971 [21] Appl.No.:210,351

[56] q References Cited UNITED STATES PATENTS 3,292,785 12/1966 Calhoun.....250/223B Primary Examiner-James Lawrence Assistant Examiner-T. N.Grigsby Attorney-Joseph F. Brisebois et a1.

[57] ABSTRACT An integrated photocell device for bottle inspectioncomprises a multiplicity of inspection photodiodes and a level sensingphotodiode, which measures the average light transmission through abottle, arranged in a suitable array for scanning an area of a bottle tobe inspected. The level sensing diode is in the form of a griddistributed over the photocell device and the inspection diodes aredisposed within the grid. The inspection diodes are each connected in anelectrical circuit which is adapted to be triggered by a pulse appliedthereto and to restore to its initial state within a time determined bythe intensity of the illumination of the photodiode. The individualinspection circuits are connected in parallel to a load resistor, theoutput voltage across which drops to zero when all the circuits haverestored to their initial states. The level sensing diode is connectedin a similar circuit to each inspection diode and is connected to aseparate load resistor. Means is provided for comparing the times takenfor the two output voltages to return to zero, after the application ofa pulse, in order to determine whether or not a bottle being scanned bythe device should be rejected as being dirty or faulty.

7 Clairm, 7 Drawing Figures DISTRlBUTE 0' LEVEL SENSING DIODE 5Q ARRAYmom-:5

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l I BOTTLE INSPECTION APPARATUS tles which are re-used after washing.

Machines are known which inspect the bottle by optically scanning thebase and/or side walls by light projec'ted therethrough. The scanningtechniques used generallyinvolve high speed rotation of the scanningmeans or bottles by electric motors. The parts are prone to wear andinspection speeds are limited. Lubricant and dust from driving belts canbe deposited on lenses and optical surfaces necessitating regularcleaning of these important components.

1 Developments in the semi-conductor art have made it possible to designarrays of photodiodes and as sociated circuitry invery small devices,which may be hermetically sealed, and the present invention has for anobject to provide apparatus for inspecting bottles or the like whichincorporates an integrated photocell device comprising an arrayofphotodiodes and associated circuitry which enables a' static inspectionsystem to be provided which is fast in operation, sensitive, reliableand requires little power for operation.

According to the invention there is provided a photocell device forbottle. inspection, comprising a plurality of photoelect'ric'meansdisposed in a suitable arrayfor scanning an area of a bottle to beinspected, each means being connected in a circuit which is triggeredupon initiation of an inspection cycle and restores to its initial'statein a time determined by the intensity of theillumination' of itsassociated photoelectricmeans, the individual circuitsbeing connected inparallel. V

The invention will be with reference.

described, by way of example, to the accompanyingdrawings, in

FIG. 1 is a circuit diagram of a photocell element comprising aphotodiode and associated circuitrysuitable for use in an integratedphotocell device according to the invention,v f

FIG. 2 shows waveforms at differentparts of the photocell element ofFIG. 1, t

'FIG. 3 shows part of the circuit of the integrated photocell device,

FIG. 4 is a diagram of one form of integrated of the MOS transistor isthat the gate input resistance is very high. This is particularly sowhen the transistor is used in the common drain or source followerconfiguration, as is T, in FIG. 1, the output voltage V being derivedacross the load resistance R Transistor T isolates the voltagesappearing on its gate G from the low impedance load resistance RTransistor T, is effectively a switch between the negative supplyvoltage Ve and the gate G of transistor T By applying a negative voltageV of sufficient amplitude to the gate of transistor T, the switch willclose and ensure that the voltage at the gate G of T will be brought toVe.

The negative voltage V applied to the gate T, is provided by a series ofcharge pulses applied to conductor A. As shown in FIG. 2 (waveform 1),these pulses are applied to the gate of transistor T, at time t,.Closing the switch causes the capacitance C, consisting of thecapacitance of the reverse-biassed photodiode P,

the input capacitance of T and stray capacitances, to be charged to thenegative voltage Ve. At time t when the charge pulse returns to zero,transistor T, switch opens, .andthe capacitance C, is isolated from thenegative supply Ve. Capacitance C (consisting of the-intrinsic and straycapacitance between the gate photocell device suitable for-inspectingthe bases of bottles,

FIG. 5 is a block circuit diagram of one embodiment of theapparatus forbottle inspection,

FIG. 6 shows the waveforms at different parts of the apparatus of FIG.5,

FIG. 7 is a schematic view of a base inspection arrangement andrejection system.

' FIG. ll shows a circuit of a photocell element suitable forincorporation in a multi-element integrated photocell device for bottleinspection apparatus according to this invention. The photocell elementcomprises a photodiode P and two P-channel enhancement metal oxidesilicon transistors (MOS transistors) T, and T connected as shown. Withsuch a transistor, no current flows in the source (S)-drain (D) circuitif the gate (G)-source voltage V is less negative than a predeterminedthreshold voltage V Another important feature and the source oftransistor T,) is also effectively connected in parallel with C,,resulting in a positive-going step in the voltage at the gateG of T(FIG. 2, waveform II),- and hence on the output voltage V (FIG. 2,waveform III) as the charges of the two capacitances re-adjust.

The total capacitance C of C, and C will start to discharge at a ratedetermined by the leakage currents through transistors T,, T, and thephotodiode P, and also the photoelectric current generated in the diode.Normally the leakage currents are insignificant compared to thephotoelectric current, therefore the rate of discharge is determined bythis current and hence the illumination on the diode.

' As C discharges, the voltage across it falls, and hence the outputvoltage V goes less and less negative until the voltage on the gate of Tbecomes less negative than V, when T, will be cut off. The outputvoltage will then be zero.

Hence, the time required for the output voltage to reach zero after theend of the charge pulse depends on the amount of light received by thediode. A dark diode takes longer to discharge the capacitance C than amore illuminated diode. I

For effecting bottle inspection in accordance with this invention alarge number of these photocell elements are built up in to a suitablyshaped array, and connected in parallel to a common load resistor. FIG.3 shows a part of the circuit of an array made up from similar elementsto those shown in FIG. 1. In order to simplify the array, points A and Bin FIG. l are connected together. This means that the charge pulses areapplied to the same conductor as that from which the output voltage isobtained.

If an image of the container area undergoing inspection is focused on tothe array and a charge pulse applied, all the T transistors will beturned on. Aftera period of time, determined by the illumination on thearray, all the transistors T, will be turned off when the voltageapplied to their gates reaches the threshold voltage V This period oftime will be substantially the same for all elements if they are allequally illuminated. If one or more of the diodes are obscured by aforeign body, the associated T transistor will not turn off within thenormal period. Thus, if the output voltage remains negative after apredetermined time period, this means that one or more of the diodes isobscured and the container being inspected should be rejected. The loadresistor and allthe T transistors effectively form an analogue OR gatewith a large number of inputs. The time required for all the Ttransistors to turn off will depend on the brightness of the lightsource and the quantity of light transmitted through the container. Inorder that both of these variables may be taken into account, theaverage light transmitted by the container is measured and the timeperiod derived from this measurement. Thus for bottles with a lowerlight transmission, or if the lamp output falls, the time allowed forthe capacitances to discharge is increased.

One method of measuring the average light transmission of the bottle isto use a circuit as shown in FIG. 1 with the photodiode distributed overthe photocell device so that the whole of the area being inspected issampled. This level sensing diode system may be integrated with thearray of photodiodes used for inspection. One such integrated photocelldevice is illustrated in FIG. 4 in which the level sensing diode is inthe form of a grid within which the array diodes are disposed. Thisparticular array, which in practice is of very small size, is suitablefor inspecting the base of a bottle.

The distributed diode circuit or level sensor circuit" has its own loadresistance and hence develops an output voltage which varies in asimilar way to that obtained from one element of the array diodes. Thedischarge time for the distributed diode is about the same as for anarray diode. This is because although the diode capacitance of thedistributed diode is increased, its area and hence the photoelectriccurrent generated are also increased. By comparing the time the levelsensor circuit takes to switch off with the time the array takes, thepresence or otherwise of foreign bodies can be determined. Normally thearray is arranged to switch off before the level sensor. If an arraydiode is obscured the level sensor will switch off first and thiscondition signifies a reject condition. This condition can be determinedby suitable logic circuitry.

If the light through a container is completely obscured or if it fallsbelow a desired minimum level due, for example, to an overall smear,then this condition is detected by comparing the time the level sensortakes to switch off with a fixed time period. Normally the level sensorwould switch off within say one millisecond. If it has not switched offafter this period, the illumination must be below the prescribed minimumand the container may be rejected if required.

The sensitivity of the array can be adjusted by adjusting the delayperiod derived from the level sensor. This can be achieved by bringingthe T gate and diode connection out of the device so that extracapacitance can be connected across C Conveniently this extracapacitance can be a small variable capacitor.

FIG. 5 shows a block diagram of one embodiment of a bottle or containerinspection system using an integrated photocell device as describedabove. The integrated photocell device 20 has the outputs from its arraydiodes at G and its level sensor diode at J fed through emitterfollowers 21, 22 to discriminating amplifiers 23, 24 respectively. Theoutput K from discriminator 24 is fed to a level bistable device 25,which is reset at the commencement of each inspection cycle, the outputsfrom 23 and 25 being fed to a NOR gate 26 so that unless the outputvoltage from the array drops to zero before that of the level sensor thebistable array reject device 27 operates and, through the NAND gate 28,produces a reject output signal.

The reset and charge pulse generator 29 is triggered by the bottleposition sensor 30 and, through the emitter follower 31, the charge andreset pulses are fed to the photocell device and other units as shown.Pulses from the generator 29 are also fed to the dark field timemonostable device 32 and reject pulse monostable device 33, the outputfrom which at D controls the width of the reject and reset outputpulses.

The output at D is also fed via inverter 34 to a NOR gate 35 to whichthe output from the level bistable device 25 is also fed, the output Qfrom gate 35 being fed to the bistable dark field reject device 36. Theinverter 37 is provided so as to enable the dark field reject circuit tobe disconnected if it be decided to eliminate this control.

FIG. 6 shows the waveforms at the various lettered positions of thecircuit shown in FIG. 5.

The inspecting system described above may, for example, be used with thebase inspection apparatus illustrated in plan in FIG. 7. In thisapparatus a queue of bottles 1 moves along the conveyor 2 and isdeflected by guide walls 3, 3a so that the bottles slide over theperipheral zone of a translucent circular plate or disc 4 which isrotated slowly by a motor (not shown) about the vertical axis 5. Beneaththe peripheral zone of the disc across which the-bottles move isdisposed the inspection light source. The disc 4 is preferably made froman opal plastics material, such as, opal polycarbonate sheet marketed byFarbenfabriken Bayer AG under the trade mark Makrolon," so as to diffusethe light from the light source. The base of the bottle is inspected bymeans of an integrated photocell device as hereinbefore describeddisposed above the mouth of the bottle, whereby to produce a rejectoutput signal if dirt, a fault or a foreign body is detected.

The upper surface of the disc is cleaned as the disc rotates, forexample by a rotary brush 6 which may be supplied with a drip feed ofdetergent, after which the disc moves under and in contact with twosqueegee wiper blades 7 and 8 between which clean rinse water is appliedto the surface of the disc at 9. The first wiper blade 7 squeegees awaythe detergent liquid and the second wiper blade 8 squeegees away therinse water.

Experiments have shown that despite the passage of the bottlesthereover, the rotation of the disc enables its upper surface to bemaintained in reasonable optical condition, whereas orientated scratchpatterns arise if the plate is stationary which can cause difficultywith the inspection. Furthermore, dirt streaks which would accumulateover a period of time and also interfere with the inspection, arecleaned away by the washing or cleaning process.

After passing the inspection zone the bottles 1 are returned to theconveyor 2, those which have produced a signal indicating dirt beingrejected from the line. In

the event of a reject output signal being produced, an electric orpneumatic actuator is operated which moves a lever arm 11 towards thebottle la in the inspection position to cause fingers 12 on the arm toproject into the pathof movement of the bottles at opposite. sides ofthe bottle la, thus arresting movement of bottle la and also of thequeue of bottles upstream the bottle is rejected, the ejector device 13and the arm 11 move back to their original positions and inspection ofthe queue of bottles again commences.

Whilst particular embodiments have been described it will be understoodthat various modifications may be made without departing from the spiritof the invention. For example, an integratedphotocell device can be usedfor inspecting the side wall of a bottle using techniques as abovedescribed with a different shape for the array.

We claim: i

l. A photocell device for inspecting transparent bottles and othercontainers comprising:

a; a multiplicity of inspection photoelectric means disposed in an arraycorresponding to an area of a container to be scanned thereby,

b. a multiplicity of electrical circuits connected respectively to saidphotoelectric means,

c. each individual circuit being adapted to be triggered by a chargepulse applied thereto and to restore to its initial state within a timedetermined by the intensity of the illumination of its associatedphotoelectric means,

d. said multiplicity of circuits being connected in parallel toinspection output .means which produces an inspection signal indicativeof when all the circuits have restored to their initial states,

and

e. charge means'for applying a charge pulse to said circuits uponinitiation of each inspection cycle.

2. A photocell device as claimed in claim 1, including level sensingphotoelectric means for measuring the average illumination of thephotocell device, said level sensing photoelectric means beingdistributed throughout the array of inspection photoelectric means sothat the whole of the area being scanned is sampled, said level sensingmeans being connected to a further electrical circuit which is adaptedto be triggered by each said charge pulse and to restore to its initialstate in a time determined by the. average illumination of said levelsensing means, and said further circuit being con- I nected to levelsensing output means which produces a level sensing signal indicative ofwhen said further circuit restores to its initial state, and means forapplying of each inspection cycle.

3. A device as claimed in claim 2, including comparing means forcomparing the time periods taken by both said output means to producesaid output signals subsequent to a char e pulse, said inspectionphotoelectric means an associated circuits being adapted normally toproduce said inspection output signal prior to said level sensing outputsignal, and said inspection output signal being subsequent to said levelsensing output signal if the illumination of any one of said inspectionphotoelectric means is obscured by dirt in a container.

4. A device 'as claimed in claim 3, including means for comparing saidtime period for said level sensing output signal with a predetermined,fixed time period, whereby to detect when the light passing through acontainer falls below a desired minimum level.

5. Adevice as claimed in claim 4, including a voltage source and whereinsaid inspection circuits and the level sensing circuit each comprisestwo MOS transistors, each of which includes source, drain and gateelectrodes, means connecting the photoelectric .connecting thesource-drain circuit of said second transistor in series with saidoutput means and across said voltage source.

6. in bottle inspection apparatus, a photocell device as claimed inclaim 5 comprising integrated inspection photodiodes and a level sensingphotodiode, said level sensing diode being in the form of a grid withinwhich the array of inspection diodes is disposed, and said integrateddiodes being in the form of a circular array adapted to scan the base ofa container being inspected and being positioned above the mouth of saidcontainer, a light source disposed below the container for illuminatingthe base thereof, and rejection means actuated in response to thecomparing means detecting dirt in the base of the container.

7. A device as claimed in claim 2, including in tegrated inspection andlevel sensing photodiodes, the level sensing diode being in the form ofa grid within which is disposed the inspection diodes, and the wholearray being of circular configuration adapted to scan the base of acontainer, a negative voltage terminal, a common terminal, and an earthterminal, each inspection circuit comprising two MOS transistors havingsource, drain and gate electrodes, means connecting an inspectionphotodiode in series with the source-drain circuit of a first one ofsaid transistors between said negative and earth terminals, meansconnecting the gate of said first transistor to said common terminal,means connecting the gate of the second transistor to the junctionbetween said first transistor and said photodiode, and means connectingthe source-drain circuit of said second transistor between said negativeand common terminals, an output load resistor connected between saidcommon and earth terminals, and

each charge pulse to said further circuit upon initiation means forapplying the charge P" to Said common

1. A photocell device for inspecting transparent bottles and othercontainers comprising: a. a multiplicity of inspection photoelectricmeans disposed in an array corresponding to an area of a container to bescanned thereby, b. a multiplicity of electrical circuits connectedrespectively to said photoelectric means, c. each individual circuitbeing adapted to be triggered by a charge pulse applied thereto and torestore to its initial state within a time determined by the intensityof the illumination of its associated photoelectric means, d. saidmultiplicity of circuits being connected in parallel to inspectionoutput means which produces an inspection signal indicative of when allthe circuits have restored to their initial states, and e. charge meansfor applying a charge pulse to said circuits upon initiation of eachinspection cycle.
 2. A photocell device as claimed in claim 1, includinglevel sensing photoelectric means for measuring the average illuminationof the photocell device, said level sensing photoelectric means beingdistributed throughout the array of inspection photoelectric means sothat the whole of the area being scanned is sampled, said level sensingmeans being connected to a further electrical circuit which is adaptedto be triggered by each said charge pulse and to restore to its initialstate in a time determined by the average illumination of said levelsensing means, and said further circuit being connected to level sensingoutput means which produces a level sensing signal indicative of whensaid further circuit restores to its initial state, and means forapplying each charge pulse to said further circuit upon initiation ofeach inspection cycle.
 3. A device as claimed in claim 2, includingcomparing means for comparing the time periods taken by both said outputmeans to produce said output signals subsequent to a charge pulse, saidinspection photoelectric means and associated circuits being adaptednormally to produce said inspection output signal prior to said levelsensing output signal, and said inspection output signal beingsubsequent to said level sensing output signal if the illumination ofany one of said inspection photoelectric means is obscured by dirt in acontainer.
 4. A device as claimed in claim 3, including means forcomparing said time period for said level sensing output signal with apredetermined, fixed time period, whereby to detect when the lightpassing through a container falls below a desired minimum level.
 5. Adevice as claimed in claim 4, including a voltage source and whereinsaid inspection circuits and the level sensing circuit each comprisestwo MOS transistors, each of which includes source, drain and gateelectrodes, means connecting the photoelectric means in series with thesource-drain circuit of a first one of said transistors and across saidvoltage source, means connecting the gate of said fiRst transistor tosaid charge pulse means, means connecting the gate of the secondtransistor to the junction between said photoelectric means and saidfirst transistor, and means connecting the source-drain circuit of saidsecond transistor in series with said output means and across saidvoltage source.
 6. In bottle inspection apparatus, a photocell device asclaimed in claim 5 comprising integrated inspection photodiodes and alevel sensing photodiode, said level sensing diode being in the form ofa grid within which the array of inspection diodes is disposed, and saidintegrated diodes being in the form of a circular array adapted to scanthe base of a container being inspected and being positioned above themouth of said container, a light source disposed below the container forilluminating the base thereof, and rejection means actuated in responseto the comparing means detecting dirt in the base of the container.
 7. Adevice as claimed in claim 2, including integrated inspection and levelsensing photodiodes, the level sensing diode being in the form of a gridwithin which is disposed the inspection diodes, and the whole arraybeing of circular configuration adapted to scan the base of a container,a negative voltage terminal, a common terminal, and an earth terminal,each inspection circuit comprising two MOS transistors having source,drain and gate electrodes, means connecting an inspection photodiode inseries with the source-drain circuit of a first one of said transistorsbetween said negative and earth terminals, means connecting the gate ofsaid first transistor to said common terminal, means connecting the gateof the second transistor to the junction between said first transistorand said photodiode, and means connecting the source-drain circuit ofsaid second transistor between said negative and common terminals, anoutput load resistor connected between said common and earth terminals,and means for applying the charge pulses to said common terminal.